Conclusion
First of all lets talk about prices. Let's consider that
the two R9 280X together cost 422 Euro. Compare that to the
849 Euro you'd have to pay for the cheapest reference NVIDIA GeForce GTX TITAN
we can find. The GTX TITAN is going to be 201 percent more expensive than the
two mid-range cards :)
To dive a bit deeper into the results, we start with performance differences in
3DMark graphics score where we see that the CrossFire of the two R9 280X is between
82 and 92 percent faster
than the NVIDIA GeForce GTX TITAN. In the next theoretical test we ran, Unigine Heaven,
we see that the two R9 280X's are on average 17 slower than the NVIDIA GTX TITAN.
In case of games it turns out that for example in Skyrim the one NVIDIA card is about 6 percent quicker than the two cards in CrossFire. A
closer look at Call of Duty Black Ops 2 shows the other end of the scale, where
the two R9 280X's score 39 percent better than the single NVIDIA GeForce GTX TITAN. In this case we see a rather huge variance in the test results.
Overall the two R9 280X cards are performing really well and there is no doubt
the two of them are seriously quick, actually, on average they're 24.8 pecent quicker than one GTX TITAN. But the problem is that the average value is not even telling half the story. It turns out that in one of the games tested the single card was quicker, then there are games where the difference is small and last but not least there are some titles where the two 280X cards are a lot faster. This in the end makes performance rather unpredictable. Other than that there is power consumption. In idle the power consumption of our test system is
104 percent higher with the two R9 280X then with one GTX TITAN and under load conditions the setup with two AMD cards can almost be used as a heating system, burning more than twice as much power. If you were to buy a new graphics cards for your system and your coming from a substantially slower environment having roughly 400 Euro at your disposal, we would, without a shadow of a doubt, recommend
two R9 280X. However, if you already own one R9 280X and you don't care about power consumption, then adding a second R9 280X to you system can boost performance in quite a few games substantially.